Cri­te­ria for Fin­ding a Donor

The human immu­ne sys­tem works accord­ing to a simp­le princip­le. Anything that doesn’t belong in the body can have harm­ful effects and is the­re­fo­re atta­cked by the cells of the immu­ne sys­tem. This is how the body defends its­elf against bac­te­ria and viru­ses. The immu­ne sys­tem is the­re­fo­re a hurd­le in the event of tis­sue trans­plan­ta­ti­on. If it regards the trans­plan­ted tis­sue or even the trans­plan­ted stem cells as for­eign, it will trig­ger a rejec­tion reac­tion. In leukemia pati­ents, the con­se­quen­ces of this can be serious and even life-threa­tening. It is the­re­fo­re extre­me­ly important to find a sui­ta­ble donor.

HLA cha­rac­te­ris­tics & gene­tic twins

To mini­mi­ze the risk of rejec­tion, it is essen­ti­al to find a donor who has the same tis­sue cha­rac­te­ris­tics as the pati­ent – a gene­tic twin. The­se cha­rac­te­ris­tics, cal­led human leu­ko­cy­te anti­gens (HLA), are tiny struc­tures on the sur­face of the cells in the body. Based on their shape, the body dis­tin­guis­hes bet­ween tho­se that belong in the body and tho­se that don’t.
The genes (blue­prints) of the five most important HLA cha­rac­te­ris­tics – A, B, C, DRB1 and DQB1 – are loca­ted on one sin­gle chro­mo­so­me and are the­re­fo­re inheri­ted joint­ly as a “haplo­ty­pe.” Every per­son inherits one HLA haplo­ty­pe from each of their par­ents. The­re are over a hund­red vari­ants of each HLA cha­rac­te­ris­tic, and the pos­si­ble com­bi­na­ti­ons reach the tril­li­on mark. Hence, the likeli­hood of fin­ding two peop­le with iden­ti­cal tis­sue cha­rac­te­ris­tics is very low and the search for a sui­ta­ble unre­la­ted donor both com­plex and elaborate.

Is it kept in the family?

The first step is to check whe­ther the­re is a gene­tic twin in the fami­ly. The likeli­hood of fin­ding a sui­ta­ble donor among sib­lings is 25%. Among other fami­ly mem­bers, the chan­ces are gene­ral­ly much lower. As fami­lies in Ger­ma­ny tend to be small, rela­ti­ves are found to be sui­ta­ble donors for appro­xi­mate­ly one third of pati­ents only, on average.

Fin­ding an unre­la­ted donor

For the remai­ning two thirds, an unre­la­ted donor must be found. The atten­ding doc­tor the­re­fo­re con­ta­cts the rele­vant search cen­ter and they agree on the search cri­te­ria. The cen­ter then for­wards all the necessa­ry infor­ma­ti­on and docu­ments to the ZKRD. The ZKRD sear­ches the natio­nal and inter­na­tio­nal donor data­ba­ses to obtain a list of poten­ti­al, sui­ta­ble donors. The search cen­ter then selects an appro­pria­te donor for the respec­ti­ve pati­ent accord­ing to defi­ned tech­ni­cal criteria.

Ques­ti­ons and answers

The most fre­quent­ly asked ques­ti­ons and ans­wers about typ­ing and stem cell dona­ti­on can be found in our FAQs.

Would you like to sign up?

Sim­ply con­ta­ct your nea­rest donor cen­ter. More infor­ma­ti­on about the donor cen­ters and their loca­ti­ons can be found on our address page.